feat: conditionally compile without a source of randomness

Cargo.toml

@@ -9,6 +9,7 @@ crate-type = ["cdylib", "rlib"]
 [features]
 default = ["getrandom"]
 getrandom = ["dep:getrandom"]
+no_random = [] # compile without access to a source of randomness
 
 [dependencies]
 getrandom = { version = "0.2", optional = true }

src/lib.rs

@@ -12,6 +12,20 @@ pub(crate) fn get_random(buf: &mut [u8]) {
     getrandom::getrandom(buf).unwrap()
 }
 
+#[cfg(feature = "no_random")]
+pub(crate) fn get_random(buf: &mut [u8]) {
+    use core::sync::atomic::{AtomicUsize, Ordering};
+    
+    static COUNTER: AtomicUsize = AtomicUsize::new(0);
+    
+    let value = COUNTER.fetch_add(1, Ordering::Relaxed);
+    let bytes = value.to_ne_bytes();
+    
+    for (i, byte) in buf.iter_mut().enumerate() {
+        *byte = bytes[i % core::mem::size_of::<usize>()];
+    }
+}
+
 /// FIXME: remove hard coded defaults
 /// The strategy for message processing is such:
 ///